In one conventional form of reactive metal-aqueous electrolyte primary battery, the cathode comprises a solid electrochemically reducible element. The anode comprises a reactive metal, such as lithium, aluminum, magnesium, etc.
Typically, the cathodes are formed of silver chloride or silver oxide. In one illustrative form, the silver chloride cathode is utilized in a magnesium-sea water battery. An example of a silver oxide battery is that utilizing an aluminum anode with a sodium hydroxide electrolyte.
In such batteries, a discharge capacity has been found to be limited by the electrochemical energy content of the cathode material. In order to maintain acceptable discharge rates, the amount of active material incorporated into the cathode is limited. Thus, illustratively, in a silver oxide cathode, the conventional maximum capacity is approximately 17 to 23 ampere-minutes per gram. Silver chloride cathodes have significantly less electrochemical energy content.
One example of a reactive metal water electrochemical cell utilizing an alkaline electrolyte is disclosed in U.S. Letters Pat. No. 4,001,043 of William R. Momyer.
Other U.S. Letters Patent disclose the use of cathode reactants, such as hydrogen peroxide, soluble nitrites or other electrochemically reducible species, such as halogens, which are added to the electrolyte and reduced at the inert metal substrate. Illustratively, such additional prior art patents include U.S. Letters Pat. No. 4,007,057, U.S. Letters Pat. No. 4,001,043 of William R. Momyer, U.S. Letters Pat. No. 4,269,907 of William R. Momyer et al, and U.S. Letters Pat. No. 3,791,871 of Leroy F. Rowley, which patents are incorporated by reference herein.
In such batteries, a serious problem arises in that the cathode reactant, being added to the flowing electrolyte, is discharged into the environment during operation. Thus, a substantial amount of the unused reactant is wasted by being discharged with the electrolyte.